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Effect of climate on growth of european larch (Larix decidua Mill.) at the upper treeline in the southeastern Alps

Abstract

Na 7 lokacijah na zgornji gozdni meji v jugovzhodnih Alpah smo preučili odvisnost med širino branike macesna (Larix decidua Mill.) in klimo. Analizo smo napravili za obdobje 1900-2003, v katerem smo ugotovili 13 skupnih pozitivnih in 17 skupnih negativnih značilnih let. Izkazalo se je, da je macesen zelo primerna drevesna vrsta za preučevanje odziva dreves na klimo. Največji vpliv na nastanek široke branike imajo nadpovprečne junijske temperature, najbolj negativen vpliv na širino branike pa nadpovprečne marčevske temperature. Analiza časovne stabilnosti klimatskega signala z odzivnimi funkcijami in metodo drsečih oken je pokazala, da se je odnos med klimo in širino branike postopoma spreminjal. Bolj ko se približujemo sedanjosti, pomembnejši postaja negativni vpliv nadpovprečnih temperatur v marcu (branike so ožje) in bolj se izgublja pomen nadpovprečne temperature v juniju. Na nekaterih ploskvah se vplivu nadpovprečnih junijskih temperatur pridruži še vpliv nadpovprečno toplega maja. Rezultati kažejo, da se na zgornji gozdni meji dogajajo spremembe v smeri zgodnejšega začetka vegetacijske sezone, s tem pa so drevesa izpostavljena večjemu tveganju poznih pozeb.The relationship between larch (Larix decidua Mill.) tree-ring widthsand climate was studied on 7 selected locations in the southeastern partof the Alps (Slovenian Alps). Analysis was performed for the 1900-2003 period, when 13 positive common and 17 negative common pointer years were identified. The response function analysis showed significant positive response (wide tree ring) of larch to above-average temperature in June and significant negative response to above-average temperature in March. Temporal stability of climate-growth relationship was tested using the Forward Evolutionary Interval Method (part of Bootstrapped response function procedurein DendroCLIM 2002). Results showed changes in response to climate asthe time approached 2003. Influence of the above-average temperature in Junewas becoming less important, while the above-average temperature in May appeared to gain importance. Besides, negative influence of the aboveaverage temperature in March was progressively gaining in its importance. Change of response is directly connected to the increasing winter temperatures at high altitudes in the last 10-15 years

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